Identification of alkane monoxygenase genes in Acinetobacter venetianus VE-C3 and analysis of mutants impaired in diesel fuel degradation

Cells of Acinetobacter venetianus strain VE-C3 are able to degrade,diesel fuel oil by a complex mechanism requiring the formation of cell aggregates and their further adhesion to fuel oil drops. In this work the biodegradation process in A. venetianus was studied by a combination of genetic, molecular and physiological methods. PCR amplification, sequencing and Southern blot analysis of alkM and rubA genes coding for the alkane hydroxylase and rubredoxin were carried out. Then, 22 Alk(-) mutants impaired in diesel fuel degradation were obtained by nitrosoguanidine mutagenesis and characterised by i) growth on alkanes as sole carbon and energy sources, ii) modification of cell electrophoretic properties, and iii) analysis of plasmid content. Data obtained revealed that the genetic determinants for alkane degradation are located on both the chromosome and the two plasmids harboured by VE-C3 strain (pAV1 and pAV2, 11 Kbp and 15 kbp, respectively). This organization of genes coding for alkane monoxygenase complex seems to be similar to the arrangement found in Acinetobacter sp. strains ADP1 and M1, where genes are scattered through the chromosome but, as a novelty, that some genes involved in hydrocarbon degradation are plasmid borne also.